While sorting through a stack of rulebooks in my warroom, I came across my original wargame rulebooks: "Rally 'Round the Flag" and "Angriff!". I got RRtF first, in the late '70's, at a small regional con at a college in PA. My parents had taken me because of my interest in Avalon Hill games, and at the con I was first exposed to miniatures gaming. The rest, as they say, is history. Heritage had a booth there and tending it was Duke Seifried himself. We asked what I needed to get started in this "miniatures gaming" thing, and he set me up with some 15mm ACW packs, basic paints, and this rulebook. Kindly purchased by my mom & dad. Needless to say, I was hooked.
A year or two later, I purchased the "Angriff!" rules as my interests expanded into WWII. Sadly, I don't remember where it came from, but I suspect a small brick and mortar hobby shop; as it became my standard procedure that whenever my parents and I traveled anywhere, I would look in the local phone book for any hobby shops and we would have to visit to see if they had anything miniatures related.
Though I haven't played "Angriff!" since the early '80's, RRtF is still a great set of rules, which I would still pull out now and then to play as late as the early '00s.